In communicating high bit rate signals over a transmission line, one general design objective is a match of the output impedance of the line driver or output buffer, the impedance of the transmission line, and the input impedance of the receiving circuit, i.e., load. If there is an impedance mismatch, unwanted results can include reduced efficiency in signal power transfer and distortion of the received signal. Associated with the reduction in signal power transfer efficiency, there can be increased power dissipation and heat at the output buffer.
Various techniques are known for matching the output impedance of the output buffer to the impedance of a transmission line. However, the known techniques are optimized to either match a fixed impedance or match at a fixed output swing, or both.